Blog Archive

25 Mar 2016

Grid-scale approach to rechargeable power storage gets new arsenal of possible materials.

Liquid metal batteries, invented by MIT professorDonald Sadoway and his students a decade ago, are a promising candidate for making renewable energy more practical. The batteries, which can store large amounts of energy and thus even out the ups and downs of power production and power use, are in the process of being commercialized by a Cambridge-based startup company, Ambri.

Now, Sadoway and his team have found yet another set of chemical constituents that could make the technology even more practical and affordable, and open up a whole family of potential variations that could make use of local resources.

The latest findings are reported in the journal Nature Communications, in a paper by Sadoway, who is the John F. Elliott Professor of Materials Chemistry, and postdoc Takanari Ouchi, along with Hojong Kim (now a professor at Penn State University) and PhD student Brian Spatocco at MIT. They show that calcium, an abundant and inexpensive element, can form the basis for both the negative electrode layer and the molten salt that forms the middle layer of the three-layer battery.

That was a highly unexpected finding, Sadoway says. Calcium has some properties that made it seem like an especially unlikely candidate to work in this kind of battery. For one thing, calcium easily dissolves in salt, and yet a crucial feature of the liquid battery is that each of its three constituents forms a separate layer, based on the materials’ different densities, much as different liqueurs separate in some novelty cocktails. It’s essential that these layers not mix at their boundaries and maintain their distinct identities.

It was the seeming impossibility of making calcium work in a liquid battery that attracted Ouchi to the problem, he says. “It was the most difficult chemistry” to make work but had potential benefits due to calcium’s low cost as well as its inherent high voltage as a negative electrode. “For me, I’m happiest with whatever is most difficult,” he says — which, Sadoway points out, is a very typical attitude at MIT.

Another problem with calcium is its high melting point, which would have forced the liquid battery to operate at almost 900 degrees Celsius, “which is ridiculous,” Sadoway says. But both of these problems were solvable.

First, the researchers tackled the temperature problem by alloying the calcium with another inexpensive metal, magnesium, which has a much lower melting point. The resulting mix provides a lower operating temperature — about 300 degrees less than that of pure calcium — while still keeping the high-voltage advantage of the calcium.

The other key innovation was in the formulation of the salt used in the battery’s middle layer, called the electrolyte, that charge carriers, or ions, must cross as the battery is used. The migration of those ions is accompanied by an electric current flowing through wires that are connected to the upper and lower molten metal layers, the battery’s electrodes.

The new salt formulation consists of a mix of lithium chloride and calcium chloride, and it turns out that the calcium-magnesium alloy does not dissolve well in this kind of salt, solving the other challenge to the use of calcium.

But solving that problem also led to a big surprise: Normally there is a single “itinerant ion” that passes through the electrolyte in a rechargeable battery, for example, lithium in lithium-ion batteries or sodium in sodium-sulfur. But in this case, the researchers found that multiple ions in the molten-salt electrolyte contribute to the flow, boosting the battery’s overall energy output. That was a totally serendipitous finding that could open up new avenues in battery design, Sadoway says.

And there’s another potential big bonus in this new battery chemistry, Sadoway says. “There’s an irony here. If you’re trying to find high-purity ore bodies, magnesium and calcium are often found together,” he says. It takes great effort and energy to purify one or the other, removing the calcium “contaminant” from the magnesium or vice versa. But since the material that will be needed for the electrode in these batteries is a mixture of the two, it may be possible to save on the initial materials costs by using “lower” grades of the two metals that already contain some of the other.

“There’s a whole level of supply-chain optimization that people haven’t thought about,” he says.

Sadoway and Ouchi stress that these particular chemical combinations are just the tip of the iceberg, which could represent a starting point for new approaches to devising battery formulations. And since all these liquid batteries, including the original liquid battery materials from his lab and those under development at Ambri, would use similar containers, insulating systems, and electronic control systems, the actual internal chemistry of the batteries could continue to evolve over time. They could also adapt to fit local conditions and materials availability while still using mostly the same components.

“The lesson here is to explore different chemistries and be ready for changing market conditions,” Sadoway says. What they have developed “is not a battery; it’s a whole battery field. As time passes, people can explore more parts of the periodic table” to find ever-better formulations, he says.

“This paper brings together innovative engineering advances in cell design and component materials within a strategic framework of ‘cost-based discovery’ that is amenable to the massive scale-up required of grid-scale applications,” says Richard Alkire, a professor of Chemical and Biomolecular Engineering at the University of Illinois, who was not involved in this research.

Because this work builds on a base of well-developed electrochemical systems used for aluminum production, Alkire says, “the path forward to grid-scale applications can therefore take advantage of a large body of existing engineering experience in areas of sustainability, environmental, life cycle, materials, manufacturing cost, and scale-up.”

The research was supported by the U.S. Department of Energy’s Advanced Research Projects Energy (ARPA-E) and by the French energy company Total S.A.

14 Jan 2016

EDMONTON, ALBERTA – SUNVAULT ENERGY INC. (“Sunvault”) announced today that in conjunction with the Edison Power Company, have completed a Smartphone Battery Case that is built initially for the IPhone. Smartphone case designs for major brands such as LG and Samsung and other Smartphone manufactured devices will follow shortly. The Company will be submitting this prototype for certification and verification in order to start to fulfill the demand that exists for this product line.

The Battery Case will provide approximately 5000 mAh (milliamp hours) of energy to the first prototype IPhone model. The Battery Case prototype will be the best performing battery case on the market because of one of its most compelling features.

That feature being that the case will charge in roughly 3 minutes and will provide approximately 200% of additional power for most smartphones that are in the average 2400 mAh battery range. As displays on Smartphones become larger and usage becomes more and more prevalent, increasing energy to these devices will be widely accepted by the pent up demand for better energy solutions by the 2 Billion Smartphone users worldwide.

In addition to the fast charging, the case will not experience or generate any significant heat, and will have the unique attributes of both a battery and Supercapacitor. Additional attributes will include superior cycles that will go far beyond the Lithium Ion spec of 500 cycles of charge / discharge before battery requires replacement. It will be considerably lighter than current products on the market and will form the perfect marriage between Smartphone requirements of protection and esthetics of a case, combined with energy release and quick recharge that is necessary for today’s enjoyment of these devices. The Company will start by focusing on the top Smartphone lines, which include: Samsung, Apple IPhone, Lenovo, LG, Huawei, Xiaomi and Sony.

Edison Power Company will be launching a KICKSTARTER campaign for all Smartphone users in the near future. Smartphone users will want to stay tuned for details of the campaign that will be further described just prior to launch. This will be a unique opportunity for Smartphone users to be first in line to receive the 5000 mAh battery case.

21 Oct 2015

Canada has a chance to add a new dimension to its energy economy – one that is clean, profitable and globally groundbreaking.

The opportunity is electricity storage, which until now has been limited by technology to a relatively modest scale. That’s about to change. And it means that Canada – and specifically Ontario – can become an ideal seedbed for storage technology, because there are ready markets for both large- and small-scale storage systems.

First, the large scale. Ontario has a fleet of nuclear generators that operate around the clock, and come close to filling the demand for power at off-peak hours. In addition, Ontario has developed a large renewable energy sector of wind and solar generation (in addition to its traditional hydro stations.) Problems sometimes arise when the natural weather cycles that drive wind and solar production are out of synch with the market cycle. On a sunny, breezy Saturday afternoon in May, with the nuclear plants running flat out, the hydro stations churning out power with the spring runoff and solar and wind systems near peak production, Ontario may have more electricity than it needs.

Our electricity system operators have a solution, of course: Sell the excess electricity to our neighbours. But since our neighbours are often in the same boat, Ontario must cut the price close to zero – or in extreme situations, even pay neighbouring states or provinces to absorb our overproduction.

Wouldn’t it make far more sense to store that excess energy, knowing that it will be needed in a matter of days, or even hours? What’s been lacking is the technology to do the job.

That’s changing however, as Ontario’s current program to procure 50 megawatts of storage capacity demonstrates. Companies with a variety of approaches are working hard to bring their solutions to market – many of them clustered at the MaRS centre in Toronto. Some, such as Hydrogenics Corp., convert electricity into hydrogen, which can be used to supplement natural gas.

My own company, NRStor, has partnered with Temporal Power and is operating a flywheel storage system in Minto, Ont., that helps the market operator to maintain consistent voltage on the grid.

Of course, businesses around the globe are looking at the same opportunities as we are, and here lies the opportunity for Canada to rebrand its energy economy.

A recent report by Deutsche Bank calls battery storage the “holy grail of solar penetration,” and believes that with the current rate of progress in improving efficiency, mass adoption of lithium ion batteries at a commercial/utility scale could occur before 2020.

Analysis by Prof. Andrew Ford of Washington State University calculates that a 1,000-megawatt air storage system from U.S.-based General Compression Inc. could deliver $6- to $8-billion of value to Ontario – in the form of lower energy costs to local utilities – over a 20-year period. All this is of interest to large-scale electricity system operators, big utilities and their customers.

But there is another reason for us to pay attention to energy storage – a reason grounded on a much more human scale. There are still large rural areas around the globe where there is no reliable electrical grid – including Northern Canada.

There is great potential for these communities, including remote First Nations communities, to improve their standard of living by installing microscale renewable generation in combination with storage, and relying less on carbon-spewing diesel generators, powered by fuel that must be transported long distances at great expense.

Storage is the key to making renewable energy a fully competitive component of any electrical grid. It can make our grid cleaner and more efficient, for the benefit of all consumers – large and small, urban and rural. We have the chance, in Canada, to become world leaders in developing this technology. Let’s seize it.

Annette Verschuren is the chairwoman and CEO of NRStor and on the board of MaRS Discovery District.

29 May 2015

Chemists at the University of Waterloo have discovered the key reaction that takes place in sodium-air batteries that could pave the way for development of the so-called holy grail of electrochemical energy storage.

Researchers from the Waterloo Institute for Nanotechnology, led by Professor Linda Nazar who holds the Canada Research Chair in Solid State Energy Materials, have described a key mediation pathway that explains why sodium-oxygen batteries are more energy efficient compared with their lithium-oxygen counterparts.

Understanding how sodium–oxygen batteries work has implications for developing the more powerful lithium–oxygen battery, which is seen as the holy grail of electrochemical energy storage. Their results appear in the journal Nature Chemistry. “Our new understanding brings together a lot of different, disconnected bits of a puzzle that have allowed us to assemble the full picture,” says Nazar, a Chemistry professor in the Faculty of Science. “These findings will change the way we think about non-aqueous metal-oxygen batteries.”

Oxygen is reduced at the surface of the cathode to form superoxide and reacts with trace water to form soluble HO2. The latter undergoes metathesis with Na+, driven by the free energy of formation of crystalline NaO2, to form cubic nuclei that crystallize from solution. Growth of the NaO2 from solution to form micrometre-sized cubes occurs via epitaxial growth promoted by phase-transfer catalysis of the superoxide from solution to the solid.

Sodium-oxygen batteries are considered by many to be a particularly promising metal-oxygen battery combination. Although less energy dense than lithium–oxygen cells, they can be recharged with more than 93 per cent efficiency and are cheap enough for large-scale electrical grid storage. The key lies in Nazar’s group discovery of the so-called proton phase transfer catalyst. By isolating its role in the battery’s discharge and recharge reactions, Nazar and colleagues were not only able to boost the battery’s capacity, they achieved a near-perfect recharge of the cell. When the researchers eliminated the catalyst from the system, they found the battery no longer worked.

Oxygen is reduced at the surface of the cathode to form superoxide and reacts with trace water to form soluble HO2. The latter undergoes metathesis with Na+, driven by the free energy of formation of crystalline NaO2, to form cubic nuclei that crystallize from solution. Growth of the NaO2 from solution to form micrometre-sized cubes occurs via epitaxial growth promoted by phase-transfer catalysis of the superoxide from solution to the solid.

“These findings will change the way we think about non-aqueous metal-oxygen batteries.” – Professor Linda Nazar Canada Research Chair in Solid-State Energy Materials University of Waterloo

Unlike the traditional solid-state battery design, a metal-oxygen battery uses a gas cathode that takes oxygen and combines it with a metal such as sodium or lithium to form a metal oxide, storing electrons in the process. Applying an electric current reverses the reaction and reverts the metal to its original form.
In the case of the sodium–oxygen cell, the proton phase catalyst transfers the newly formed sodium superoxide (NaO2) entities to solution where they nucleate into well-defined nanocrystals to grow the discharge product as micron-sized cubes.The dimensions of the initially formed NaO2 are critical; theoretical calculations from a group at MIT has separately shown that NaO2 is energetically preferred over sodium peroxide, Na2O2 at the nanoscale.

When the battery is recharged, these NaO2 cubes readily dissociate, with the reverse reaction facilitated once again by the proton phase catalyst. Chemistry says that the proton phase catalyst could work similarly with lithium-oxygen. However, the lithium superoxide (LiO2) entities are too unstable and convert immediately to lithium peroxide (Li2O2). Once Li2O2 forms, the catalyst cannot facilitate the reverse reaction, as the forward and reverse reactions are no longer the same.

So, in order to achieve progress on lithium–oxygen systems, researchers need to find an additional redox mediator to charge the cell efficiently. ”We are investigating redox mediators as well as exploring new opportunities for sodium–oxygen batteries that this research has inspired,” said Nazar. “Lithium–oxygen and sodium-oxygen batteries have a very promising future, but their development must take into account the role of how high capacity – and reversibility – can be scientifically achieved.” Postdoctoral research associate Chun Xia along with doctoral students Robert Black, Russel Fernandes, and Brian Adams co-authored the paper.
The ecoENERGY Innovation Initiative program of Natural Resources Canada, and the Natural Sciences and Engineering Research Council (NSERC) of Canada funded the project.